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THERMONUCLEAR IGNITION 13plasma compression, is a source of additional heating, occurring in amanner analogous to that which occurs in the adiabatic compression ofa gas. Other methods of additional heating, particularly the microwavepowerinjection method, can be applied to the Ignitor through a certainnumber of access ports in the plasma chamber.These heating methods along with ohmic heating are sufficient toachieve ignition conditions. The additional power required still remainsrelatively modest thanks to the reduced dimensions of the device. Thishas been verified with numerical calculations by means of a code thatcan simulate the discharge in a tokamak-typc device (transport code).Such a code contains a plasma model that takes into account, in themost accurate manner possible, the various processes by which theplasma loses energy.Such processes can be divided into three categories:Losses by Emission of Electromagnetic RadiationAmong these are processes like bremsstrahlung and cyclotron radiation,which can be accurately evaluated. The radiation loss from heavyimpurities, on the other hand, is difficult to evaluate, since this dependscritically on the concentration of the impurities, which is difficult toanticipate. The concentration is in turn dependent on the effects thatthe metallic walls of the plasma chamber are subjected to by the plasmadensity, the presence of density and temperature lluctuations, and thelike."Classical Transport" Processes from theCollision between the Plasma ParticlesThese depend on the various collisions' frequencies and give rise to athermal conductivity of which many aspects can be compared to thoseof ordinary gases. The energy loss produced by these processes tends todecrease with an increase in the temperature and values that can be wellcontrolled."Anomalous" LossesThese depend on the collective modes of the plasma and not on theelfects of the collisions among single particles. By collective modes aremeant waves, fluctuations in density and temperature, convective cells,and the like, that can be excited spontaneously in the plasma column.For example, it is reasonable to expect that the amplitude of the densityand temperature lluctuations increases with the increase in the plasma'smean temperature. Yet the effects of the collective modes are nottheoretically well understood at present, and only the experimentalrealization of D--T plasmas in which the heating of the alpha particles